Travelers take a variety of approaches to navigate between a trip's origin and destination. In one of the most basic approaches, a driver carries a conventional map as a navigation aid and references the map during the trip. Many people find the graphic content of a map, which is presented from a bird's-eye perspective, unfamiliar and cumbersome. Others are overwhelmed by too much information or find the print is too small.
Either as a supplement for a map or as a replacement, a person who is familiar with a route often composes driving instructions from memory and communicates them to a driver. The driver uses a written copy of the instructions as a guide to following the route. People who have driven a route tend to compose instructions that are aligned with the natural driving perspective. Good directions or driving instructions describe intersections concisely, accurately, and without prolix. If a route for a given set of driving instructions crosses an intersection that a driver would naturally ignore, a good set of driving instructions tend not to provide any extraneous instructions or description for that intersection. For example, a good set of driving instructions usually would not describe ten roads that intersect a route over a short distance such as a quarter mile prior to a turn instruction.
Good driving instructions usually attempt to match a driver's perspective. Drivers tend to perceive intersections and route components in relation to other elements in their field of view. Since people who give directions or driving instructions are often drivers themselves, they tend to describe intersections in a context aligned to a driver's forward-viewing perspective. For example, to guide a driver through an intersection with complex road geometry, a person tends to describe a route to a destination based on its geometric orientation relative to another intervening road.
In certain circumstances when a segment of a route includes two intersections in close proximity to one another, a driver may perceive the intersections as one integrated route component. People who provide driving directions or instructions tend to intuitively recognize the underlying conditions and, when appropriate, provide a single instruction to guide a driver through both intersections.
While the human based approach to navigation has benefits, it has significant limitations. In many cases, a driver simply cannot access anyone with familiarity of a route or a particular destination. And while human based driving instructions are usually the easiest to follow by a driver, frequently humans can remember or describe routes inaccurately. Human-generated instructions can be susceptible to human error. And, since individual perception is subjective, the quality and consistency of human-generated instructions can vary greatly.
As an alternative to the human based driving directions or instructions, computers can routinely generate driving instructions via conventional technologies. Commercial sources, including Internet websites and stand-alone software packages, offer a driver a list of instructions, or a driving itinerary, between one location and another. Conventional computer-generated driving instructions are generally more consistent than human-generated instructions. And with the recent proliferation of mobile computing and Internet technologies, computer-generated driving instructions are reasonably accessible in many driving situations.
Computers conventionally derive driving directions from commercially available databases that contain the geographic location of roads and intersections in a region. For each road, the database identifies name, type, speed limit, allowable direction of travel, and turn restrictions. “Shape points” identify the path of a road between “nodes,” such as an intersection, state line, name change, or other defining feature.
Conventional mapping software generates a route between user-selected start and destination points by processing the commercial database. The software typically displays a route by highlighting it on a traditional map and displaying the highlighted map through a user interface. To accompany the map, conventional software can generate textual driving instructions with what can be referred to as an itinerary module. Conventional itinerary modules process the route rather than the database per se.
While conventional mapping software is frequently accessible and generally produces consistent directions, its instructions differ from those of a human instruction giver. Conventional computer-generated driving instructions typically lack the natural, human perspective of a driver. Conventional computer software may output unneeded instructions at intersections that an ordinary driver could navigate solely on the basis of a natural driving perspective. Extraneous instructions may not be helpful to a driver. Furthermore, conventional software may not output needed instructions for confusing intersections that an ordinary driver could not readily navigate on the sole basis of natural driving perspective. The software also may output a series of choppy instructions to describe closely spaced intersections.
A driver attempting to navigate a route by following such instructions may not have time between each intersection to read each instruction. Furthermore, conventional computer-generated driving instructions do not typically emulate natural human language. The language may be choppy, overly wordy, or structurally confusing. Such language can distract a driver attempting to navigate a route in busy traffic on unfamiliar roadways.
In many instances, it would be desirable to provide driving directions with the positive attributes of both human-generated and computer-generated directions, but without the negative attributes of either. Accordingly, there is a need in the art for a computer-based method and system for generating clear, concise driving instructions that emulate natural language and conform to the human driving perspective.